Chromosomal mapping of the prolactin/growth hormone gene family in the mouse

A useful model to compare human and mouse growth hormone gene chromosomal structure, expression and regulation, and immune tolerance of human growth hormone analogues

Human (h) pituitary growth hormone (GH) is both physiologically and clinically important. GH reaches its highest circulatory levels in puberty, where it contributes to energy homeostasis and somatogenic growth. GH also helps to maintain tissues and organs and, thus, health and homeostasis. A reduction in the rate of hGH production begins in middle age but if GH insufficiency occurs this may result in tissue degenerative and metabolic diseases. As a consequence, hGH is prescribed under conditions of GH deficiency and, because of its lipolytic activity, stimulation of hGH release has also been used to treat obesity. However, studies of normal GH production and particularly synthesis versus secretion are not feasible in humans as they require sampling normal pituitaries from living subjects. Furthermore, human (or primate) GH structure and, as such, regulation and potential function, is distinct from non-primate rodent GH. As a result, most information about hGH regulation comes from measurements of secreted levels of GH in humans. Thus, partially humanized hGH transgenic mice, generated containing fragments of human chromosome 17 that include the intact hGH gene locus and many thousands of flanking base pairs as well as the endogenous mouse (m) GH gene provide a potentially useful model. Here we review this mouse model in terms of its ability to allow comparison of hGH versus mGH gene expression, and specifically: (i) GH locus structure as well as regulated and rhythmic expression; (ii) their ability to model a clinical assessment of hGH production in response to overeating and hyperinsulinemia as well as a possible effect of exercise, and (iii) their hGH-related immune tolerance and thus potential for testing hGH-related analogue immunogenicity.

STAT5 and prolactin participate in a positive autocrine feedback loop that promotes angiogenesis

We have shown previously that the murine prolactin/growth hormone family member proliferin plays a pivotal role in angiogenesis induced by the FGF2/STAT5 signaling cascade. To delineate the signaling pathway downstream of STAT5 in the human system, where proliferin does not exist, we expressed constitutively active (CA) or dominant-negative (DN) mutant STAT5A in hCMEC/D3 human brain endothelial cells. We found that conditioned medium from CA-STAT5A- but not from DN-STAT5A-overexpressing endothelial cells (EC) is sufficient to induce EC migration and tube formation but not proliferation, indicating that STAT5A regulates the secretion of autocrine proangiogenic factors. We identified prolactin (PRL) as a candidate autocrine factor. CA-STAT5A expression stimulates PRL production at the RNA and protein level, and STAT5A binds to the PRL promoter region, suggesting direct transcriptional regulation. Medium conditioned by CA-STAT5A-overexpressing EC induces phosphorylation of the PRL receptor and activates MAPK. Knockdown of PRL expression by shRNA or blocking of PRL activity with neutralizing antibodies removed the CA-STAT5A-dependent proangiogenic activity from the conditioned medium of EC. The addition of recombinant PRL restores this activity. STAT5A-induced PRL in the conditioned medium can activate STAT5, STAT1, and to a lesser extent STAT3 in hCMEC/D3 cells, suggesting the existence of a positive feedback loop between STAT5 and PRL that promotes angiogenesis. Furthermore, we find that VEGF, a potent proangiogenic factor, is induced by activation of STAT5A, and VEGF induction depends on PRL expression. These observations demonstrate a STAT5/PRL/VEGF signaling cascade in human brain EC and implicate PRL and VEGF as autocrine regulators of EC migration, invasion, and tube formation.

Spatial and temporal expression of the 23 murine Prolactin/Placental Lactogen-related genes is not associated with their position in the locus

Background

The Prolactin (PRL) hormone gene family shows considerable variation among placental mammals. Whereas there is a single PRL gene in humans that is expressed by the pituitary, there are an additional 22 genes in mice including the placental lactogens (PL) and Prolactin-related proteins (PLPs) whose expression is limited to the placenta. To understand the regulation and potential functions of these genes, we conducted a detailed temporal and spatial expression study in the placenta between embryonic days 7.5 and E18.5 in three genetic strains.

Results

Of the 22 PRL/PL genes examined, only minor differences were observed among strains of mice. We found that not one family member has the same expression pattern as another when both temporal and spatial data were examined. There was also no correlation in expression between genes that were most closely related or between adjacent genes in the PRL/PL locus. Bioinformatic analysis of upstream regulatory regions identified conserved combinations (modules) of putative transcription factor binding sites shared by genes expressed in the same trophoblast subtype, supporting the notion that local regulatory elements, rather than locus control regions, specify subtype-specific expression. Further diversification in expression was also detected as splice variants for several genes.

Conclusion

In the present study, a detailed temporal and spatial placental expression map was generated for all murine PRL/PL family members from E7.5 to E18.5 of gestation in three genetic strains. This detailed analysis uncovered several new markers for some trophoblast cell types that will be useful for future analysis of placental structure in mutant mice with placental phenotypes. More importantly, several main conclusions about regulation of the locus are apparent. First, no two family members have the same expression pattern when both temporal and spatial data are examined. Second, most genes are expressed in multiple trophoblast cell subtypes though none were detected in the chorion, where trophoblast stem cells reside, or in syncytiotrophoblast of the labyrinth layer. Third, bioinformatic comparisons of upstream regulatory regions identified predicted transcription factor binding site modules that are shared by genes expressed in the same trophoblast subtype. Fourth, further diversification of gene products from the PRL/PL locus occurs through alternative splice isoforms for several genes.

Adaptive evolution of the first extra exon in the murid rodent prolactin gene family

The prolactin gene family in rodents consists of multiple members that coordinate the processes of reproduction and pregnancy. Some members of this family acquired one or two additional exons between exon 2 and exon 3 of the prototypical 5-exon, 4-intron structure, but the evolutionary importance of this insertion is unclear. Here, we focus on those members and survey this question by molecular evolutionary methods. Phylogenetic analysis shows that those members cluster into two distinct groups. Further analysis shows that the two groups of genes originated before the divergence of mouse and rat but after that of rodents from other mammals. We compared the d (N)/d (S) values for each branch of the gene tree but found no evidence to support positive selection for any branch. We found strong evidence, however, that one site (11E) of the 13 sites of the first extra exon underwent positive selection by the site-specific models of the maximum-likelihood method. Combining our molecular evolutionary analysis with other known functional evidence, we believe that the insertion of the extra exon implies some functional adaptation.

Molecular Evolution of Prolactin Gene Family in Rodents

In this study, we identified two novel members of prolactin gene family in rat by blast searches against the published genomic database. A further analysis showed that gene duplications leading to PRL gene family in rodents occurred after rodents diverged from other mammals. Major reorganization of the gene loci in rodents was largely completed before the split of rat and mouse. But PL-I and PL-II genes are the exceptions, which have clustered in a species-specific manner in the phylogenetic tree. By combining results from gene conversion testing, relative chromosomal location comparison and estimated time for gene duplication, we believe that rodent PL-1 and PL-II genes are species-specific and are the results of serial duplications which occurred after the divergence of mouse and rat. Our analysis also reveals that continual gene duplication and divergence occurred during the evolution of rodent PRL gene family.

Mitogen-regulated protein/proliferin mRNA induction following single applications of tumor promoters to murine skin

Mitogen-regulated protein/proliferin (mrp/plf) gene family transcripts rise in abundance as a response to diverse chemical and physical agents that promote morphological transformation in the murine C3H/10T1/2 cultured cell model of multi-step carcinogenesis. To determine if proliferin genes respond to tumor promoters in vivo, RNA was extracted from the whole skin of SENCAR mice after single applications of 2 or 20 microg 12-O-tetradecanoylphorbol-13-acetate (TPA); 3.2 or 32 nmole), 20 or 40 mg benzoyl peroxide (BPO; 83, 165 micromole), or acetone vehicle alone (2.72 mmole). RNA samples were prepared from treated skin areas, 2-48 h after painting. Mrp/plf-mRNA was not detected in Northern blot hybridizations, but large increases in mRNAs for ornithine decarboxylase gene and mRNA (odc), v-jun oncogene-related transcription factor gene and mRNA (junB), egr1 (early growth response protein gene and mRNA) were measured relative to beta 2 microglobulin gene and mRNA (b2m) mRNA in response to TPA. BPO induced small relative changes in these mRNAs. Reverse transcriptase (RT)-polymerase chain reactions (PCR) detected fully-processed MRP/plf-mRNA 16-48 h after TPA treatments in five of six animals, and in three of six BPO-treated animals. The MRP/plf-mRNA species expressed in the skin were predominantly plf1 and mrp3 as determined by gene-specific restriction enzyme sites within the RT-PCR products. Expression was either undetectable or found at low levels in acetone-painted controls and was not detected during the anagen phase of the normal hair growth cycle in unpainted animals. These results demonstrate that mrp/plf-mRNA is differentially expressed in murine skin in response to mechanistically distinct tumor promoters and has potential utility as a short-term biomarker for tumor promoting effects in chemical carcinogenesis.

Organization and evolution of a gene-rich region of the mouse genome: a 12.7-Mb region deleted in the Del(13)Svea36H mouse

Del(13)Svea36H (Del36H) is a deletion of approximately 20% of mouse chromosome 13 showing conserved synteny with human chromosome 6p22.1-6p22.3/6p25. The human region is lost in some deletion syndromes and is the site of several disease loci. Heterozygous Del36H mice show numerous phenotypes and may model aspects of human genetic disease. We describe 12.7 Mb of finished, annotated sequence from Del36H. Del36H has a higher gene density than the draft mouse genome, reflecting high local densities of three gene families (vomeronasal receptors, serpins, and prolactins) which are greatly expanded relative to human. Transposable elements are concentrated near these gene families. We therefore suggest that their neighborhoods are gene factories, regions of frequent recombination in which gene duplication is more frequent. The gene families show different proportions of pseudogenes, likely reflecting different strengths of purifying selection and/or gene conversion. They are also associated with relatively low simple sequence concentrations, which vary across the region with a periodicity of approximately 5 Mb. Del36H contains numerous evolutionarily conserved regions (ECRs). Many lie in noncoding regions, are detectable in species as distant as Ciona intestinalis, and therefore are candidate regulatory sequences. This analysis will facilitate functional genomic analysis of Del36H and provides insights into mouse genome evolution.

The prolactin and growth hormone families: pregnancy-specific hormones/cytokines at the maternal-fetal interface

The prolactin (PRL) and growth hormone (GH) gene families represent species-specific expansions of pregnancy-associated hormones/cytokines. In this review we examine the structure, expression patterns, and biological actions of the pregnancy-specific PRL and GH families.

Combined effects of tumor promoters and serum on proliferin mRNA induction: a biomarker sensitive to saccharin, 2,3,7,8-TCDD, and other compounds at minimal concentrations promoting C3H/10T1/2 cell transformation

Increases in proliferin (PLF) gene family mRNA abundance and promotional effects in cell transformation assays are paired responses that follow exposures to diverse chemical and physical agents in the C3H/10T1/2 in vitro model of multi-stage carcinogenesis. This study measured PLF mRNA abundance changes over 1 to 3 d in response to several types of promoters that were previously unassessed for this effect. Saccharin is a known promoter of cell transformation in C3H/10T1/2 cell cultures, but unlike 12-O-tetradecanoylphorbol 13-acetate (TPA) or mezerein, PLF mRNA abundance increases were inconsistently detected following simple addition of saccharin to the culture medium. Consistent effects occurred when pretreatments with promoting concentrations of saccharin or sodium saccharin (1-13 mM) were combined with subsequent additions of serum or complete medium changes. When added at or near their lowest observed effect levels (LOELs) for transformation, other promoters of 10T1/2 cells such as formaldehyde (50-100 microM), diethylstilbesterol (DES) (0.5-30 microM), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) (4-40 pM) were shown to be inducers of both basal and serum-induced PLF mRNA levels. Acetaldehyde (300-900 microM) was comparable to formaldehyde as an inducer. In contrast to these various promoters, pretreatment with phenobarbital or methanol, both non-promoters in these cells, did not affect serum-induced PLF mRNA levels at concentrations up to 3 mM and 2 M, respectively. The published values for the LOELs of 17 promoters of cell transformation and the LOELs determined to date for PLF mRNA induction were highly correlated over a 1 billion - fold concentration range. The response of PLF mRNA is a short-term marker sensitive to the active concentration ranges of diverse chemical agents with promotional activity in C3H/10T1/2 cell transformation system.

The mouse prolactin gene family locus

In the mouse, there is a large family of paralogous genes closely related to PRL. The objective of this report was to investigate the organization of the mouse PRL gene family locus. PRL family genes reside on chromosome 13 of the mouse genome. The PRL gene family members were localized to a series of overlapping bacterial artificial chromosome clones and arranged based on structural relationships. Additionally, several new members of the PRL gene family were identified. Placental lactogen I (PL-I) was found to be encoded by three closely related (>98% exon sequence identity) contiguous genes (termed: PL-Ialpha, PL-Ibeta, and PL-Igamma). Two previously unidentified mouse orthologs for members of the rat PRL family, PRL-like protein-I (PLP-I) and PLP-K were discovered, as were two new members of the PLP-C subfamily, PLP-Cgamma and PLP-Cdelta, and two new entirely unique members of the PRL family, PLP-N and PLP-O. Amino acid sequences predicted from the latter two genes most closely resembled proliferin-related protein. Each of the nine newly discovered genes is expressed in trophoblast cells of the mouse placenta in a gestationally specific pattern. In summary, elucidation of the mouse PRL gene family locus provides new insights into the expansion of the mouse PRL family and new tools for studying the genetics and biology of its members.

Mrp3, a mitogen-regulated protein/proliferin gene expressed in wound healing and in hair follicles

During cutaneous wound healing, a marked increase in the local expression of growth factors results in increased migration and proliferation of the cells responsible for tissue repair. The mitogen-regulated protein (MRP)/proliferin proteins are growth factors and angiogenesis factors. Here it is demonstrated that Mrp3 is induced in wound edge keratinocytes during cutaneous wound healing and also temporally appears in the outer root sheath of the hair follicle during the late anagen phase of the hair cycle. In cultured keratinocytes, Mrp3 is induced by keratinocyte growth factor, but not by epidermal growth factor or by transforming growth factor type alpha. Transgenic mice, expressing lacZ under the combined control of the cytomegalovirus immediate early enhancer and the Mrp3 flanking sequences, demonstrate wound- and hair cycle-induced transgene expression. These results show that elements within the flanking regulatory sequences of the Mrp3 gene are involved in the activation of Mrp3 in response to these events. The results reported here suggest that MRP3 may participate in wound healing and hair follicle cycle as a growth factor and/or angiogenesis factor.

Prolactin (PRL)-like protein J, a novel member of the PRL/growth hormone family, is exclusively expressed in maternal decidua

A search of a nonmouse, nonhuman, expressed sequence tag database for messenger RNAs in the PRL/GH family has identified a novel rat complementary DNA clone. The encoded protein, designated PRL-like protein J (PLP-J), is predicted to be synthesized as a precursor of 211 amino acids, modified by N-linked glycosylation, and secreted as a mature glycoprotein of 182 residues. PLP-J messenger RNA synthesis is limited to early pregnancy with abundant expression on day 7, slightly declining expression on day 9, and no detectable expression by day 11. Unlike most other PRL family members, PLP-J does not appear to be synthesized by placental trophoblasts but, rather, by decidual cells surrounding the implantation site. By sequence similarity to rat PLP-J, a murine clone was identified in a mouse expressed sequence tag database. Mouse PLP-J was used to map the gene to a 700-kb region of mouse chromosome 13 that includes other members of the PRL/GH family.

Evidence for evolutionary conservation of a physical linkage between the human BAF60b, a subunit of SWI/SNF complex, and thyroid hormone receptor interacting protein-1 genes on chromosome 17

The ubiquitously expressed rat BAF60b gene, which codes for a subunit of the multiprotein SWI/SNF complex, was recently identified between the pituitary growth hormone (GH-N) and thyroid hormone receptor interacting protein-1 (TRIP-1) genes. In primates, duplication of the GH-N gene has resulted in the addition of four placenta-specific (GH-V, CS-A, CS-B, and CS-L) genes downstream of the GH-N gene. As part of our study of the effect of remote sequences on the transcriptional regulation of the GH/CS gene family, we showed recently that these genes lie 40 kb upstream of the human TRIP-1 gene. We have now investigated the presence of the human BAF60b gene upstream of the TRIP-1 gene for evidence of evolutionary conservation of this arrangement or its disruption by the recent duplication of the nearby GH-N gene in primates. We report that, as in the rat genome, the human BAF60b gene is in the reverse transcriptional direction relative to the TRIP-1 gene, such that their polyadenylation sites are separated by 93 bp which compares with 92 bp in the rat. Reexamination of reported porcine TRIP-1 sequences also revealed the presence of the BAF60b gene separated by 93 bp, supporting an evolutionary conservation of this arrangement.Key words: P1 clone, gene mapping, downstream gene.

A new member of the mouse prolactin (PRL)-like protein-C subfamily, PRL-like protein-C alpha: structure and expression

In this study, we establish the presence of a unique member of the PRL-like protein-C (PLP-C) subfamily in the mouse, PLP-C alpha, characterize its complementary DNA and gene, and map its chromosomal location and pattern of expression during pregnancy. Mouse PLP-C alpha encodes for a 239 amino acid protein and possesses from 69-71% identity with rat PLP-C, PLP-Cv, PLP-D, and PLP-H. Another feature characteristic of PLP-C subfamily members that is also present in mouse PLP-C alpha is a 6-exon/5-intron gene structure including an aromatic domain encoded by exon 3. Southern analysis with mouse and rat PLP-C subfamily probes suggested the existence of a single mouse PLP-C alpha gene. Mouse PLP-C alpha maps to chromosome 13 along with other members of the mouse PRL family. Expression of mouse PLP-C alpha increases dramatically as gestation advances and is restricted to spongiotrophoblast and trophoblast giant cells of the junctional zone. In summary, we have established the presence of a new PLP-C subfamily member in the mouse and demonstrated its similarity in structure and expression to rat PLP-C subfamily members. This level of conservation between species expands the biological significance of the PLP-C subfamily and provides additional opportunities for genetically evaluating its function.

Calcyclin in the mouse decidua: expression and effects on placental lactogen secretion

Placental lactogens are protein hormones produced by the placentas of many mammals. These hormones have diverse reproductive functions and are structurally similar to the pituitary hormones growth hormone and prolactin. Isolated decidual cells were previously shown to release a protein that stimulates mouse placental lactogen (mPL)-II release from mouse trophoblast cells in culture. Partial amino acid sequence data suggested that this protein shared sequence identity with mouse calcyclin. In the present study the sequence identity of this protein was determined by sequencing reverse transcription-polymerase chain reaction (RT-PCR) products. The sequence matched that of mouse calcyclin. The distribution of calcyclin message was determined in the conceptus by in situ hybridization, and a gestational profile of calcyclin mRNA was determined by Northern blot analysis. Calcyclin was localized primarily to cells that exhibited a uterine natural killer cell morphology within the decidua and to glycogen cells of the labyrinth and junctional zone. Although calcyclin was detectable by RT-PCR in midterm placentas, isolated trophoblast cells in culture did not contain detectable quantities of calcyclin by RT-PCR. Calcyclin stimulated secretion of mPL-II from isolated trophoblast cells in vitro but did not affect mPL-I secretion.

Two novel members of the prolactin/growth hormone family are expressed in the mouse placenta

Two novel members of the mouse PRL/GH family have been identified through a search of an expressed sequence tag database. The encoded proteins do not appear to be homologs of other known members of this hormone family. One of these proteins, designated PRL-like protein E (PLP-E), is predicted to be synthesized as a precursor of 265 amino acids, modified by N-linked glycosylation, and secreted as a mature glycoprotein of 236 residues. The second clone encodes a protein of 253 residues with consensus sites for N-linked glycosylation; the secreted form of the protein, designated PRL-like protein F (PLP-F), is predicted to be 223 amino acids in length. Both of these messenger RNAs are expressed specifically in the placenta, with peak levels of PLP-E on days 10-12 and of PLP-F on days 14-16. Expression of PLP-E is restricted to the trophoblast giant cells, whereas PLP-F is synthesized only in the spongiotrophoblasts. The genes for both of these proteins map to a 700-kilobase region of mouse chromosome 13 that includes other members of the PRL/GH family.

Three new members of the mouse prolactin/growth hormone family are homologous to proteins expressed in the rat

A search of a mouse expressed sequence tag database for novel messenger RNAs (mRNAs) in the PRL/GH family has identified three clones that are homologous to the rat PRL-like protein A (PLP-A), PRL-like protein B (PLP-B), and decidual/trophoblast PRL-related protein (d/tPRP). Full-length complementary DNA clones for each of these three mouse mRNAs have been sequenced. Mouse PLP-A is predicted to be synthesized as a precursor of 227 residues and secreted as a glycoprotein of 196 amino acids; the secreted protein shares 78% identity with rat PLP-A. The open reading frame for mouse PLP-B encodes a protein of 230 residues; the putative mature glycoprotein of 201 amino acids is 66% identical to rat PLP-B. The third mouse complementary DNA clone encodes a precursor protein of 240 residues and a secreted glycoprotein of 211 amino acids with 64% identity to rat d/tPRP. All three mouse mRNAs are expressed specifically in the placenta or decidua. The highest levels of the PLP-A mRNA are detected on day 12, at which time expression is localized to a subset of trophoblast giant cells, especially those cells that line maternal blood sinuses. PLP-B mRNA levels are high on day 10 in decidual cells and on day 12 in spongiotrophoblasts. The mRNA similar to rat d/tPRP is present at high levels even earlier in gestation (day 8) and is localized to the decidual layer. The identification of PRL-related mRNAs in common between the mouse and rat indicates that the encoded hormones are evolutionarily conserved and, therefore, likely to play important roles in reproductive physiology.

Identification and characterization of a mouse homolog for decidual/trophoblast prolactin-related protein

Decidual/trophoblast PRL-related protein (d/tPRP) is one member of a large placental PRL gene family composed of at least nine members in the rat and four in the mouse. Only placental lactogen I and II have been characterized in both rat and mouse. The identification of mouse homologs for rat placental PRL family members will facilitate gene manipulation studies aimed at identifying functions for these hormones. In this report, we establish the presence of d/tPRP in the mouse and characterize its complementary DNA, protein, and pattern of expression during mouse gestation. Evaluation of the National Center for Biotechnology Information database of expressed sequence tags resulted in the identification of several mouse complementary DNA clones exhibiting significant homology to rat d/tPRP. One of these clones was obtained from IMAGE Consortium and Research Genetics for further investigation. The full-length mouse clone was found to have an 81% nucleotide homology with rat d/tPRP and to encode a 239-amino acid protein. Like rat d/tPRP, the mouse protein contains two putative N-linked glycosylation sites and six homologously located cysteine residues. Mouse d/tPRP maps to chromosome 13 along with other members of the mouse PRL family. Like the rat, mouse d/tPRP messenger RNA and protein are expressed by antimesometrial decidual cells and spongiotrophoblast and trophoblast giant cells in the junctional zone of the placenta. In summary, we have established the presence of d/tPRP in the mouse and demonstrated its similarity in structure and pattern of expression to rat d/tPRP. This level of conservation between species expands the biological significance of d/tPRP during pregnancy and provides additional opportunities for evaluating its function.

Construction of a 3-Mb contig and partial transcript map of the central region of mouse chromosome 11

We report the establishment of a high-resolution genetic map, a physical map, and a partial transcript map of the Ames dwarf critical region on mouse chromosome 11. A contig of 24 YACs and 13 P1 clones has been assembled and spans approximately 3 Mb from Flt4 to Tcf7. A library of approximately 1000 putative transcript clones from the region was prepared using exon amplification and pituitary cDNA selection. Ten novel transcripts were partially characterized, including a member of the olfactory receptor family, an alpha-tubulin-related sequence, and a novel member of the cdc2/CDC28-like kinase family, Clk4. The location of Prop1, the gene responsible for Ames dwarfism, has been localized within the contig. This contig spans a region of mouse chromosome 11 that exhibits linkage conservation with human chromosome 5q23-q35. The strength of the genetic map and genomic resources for this region suggest that comparative DNA sequencing of this region could reveal the genes responsible for other mouse mutants and human genetic diseases.

Chromosome localization of the gene for growth hormone in the common shrew (Sorex araneus)

The chromosome localization of the gene encoding growth hormone (GH) was determined by Southern blotting of DNA obtained from a panel of common shrew x Chinese hamster and common shrew x mouse hybrid somatic cell clones using mink GH DNA as a probe. The GH gene was found to be localized on chromosome hn of the common shrew.

Expression of different mitogen-regulated protein/proliferin mRNAs in Ehrlich carcinoma cells

Results from in vivo and from serum-free primary cultures of Ehrlich cells suggest that the expression of mitogen-regulated protein/proliferin (MRP/PLF) mRNAs is not essential for proliferation of this murine tumor. Two sizes for MRP/PRL-related open reading frames (ORFs) have been detected by reverse transcription/PCR amplification. They are almost identical to that reported for PLF-1; but 20% of the amplified cDNA included a shorter ORF, which lacks the entire sequence corresponding to that of the exon 3 of the mrp/plf genes. Ehrlich carcinoma may represent a good model to study regulation of expression and physiological roles of MRP/PLFs in vivo.

Bovine placental prolactin-related hormones

The bovine placenta, like that of rodents and primates, synthesizes members of the PRL/GH gene family, which may assist the pituitary hormones or perform unique functions during pregnancy. Bovine placental lactogen (bPL) potentially may act through.three receptors: as an agonist or partial antagonist at the PRL and GH receptors, and via an apparently specific receptor in the endometrium. A large distinct subfamily of diverse primary structure, including bovine PRL-related protein I (bPRP-I), evidently does not act via these receptors. Advances in our understanding of hormone-receptor interactions for this gene family have provided new tools to study the role of these hormones in the successful pregnancy.

Somatic cell mapping, polymorphism, and linkage analysis of bovine prolactin-related proteins and placental lactogen

The bovine prolactin gene family includes novel members expressed in the fetal placenta that are distinct from placental lactogen. In this study, we investigated the genetic organization of four members of this gene family (PRP1, PRP3, PRP6, and PRP10) as well as placental lactogen (PL). Using a bovine-rodent hybrid somatic cell panel, all five genes were assigned to bovine chromosome 23, which contains prolactin and the major histocompatibility group (BOLA). Restriction fragment length polymorphisms were detected by all probes in breeding populations with the restriction enzyme MspI, whereas no polymorphisms were detected with BamHI. EcoRI, HindIII, TaqI, and PstI produced polymorphic fragments with some but not all of the probes tested. A PRP10 polymorphism, which is apparently the result of a insertion/deletion event, detected polymorphism frequency differences between Bos indicus and Bos taurus. No recombinational events were observed with these probes and prolactin using linkage analysis involving 91 American Holsteins. The bovine prolactin gene family was incorporated into a linkage group containing CYP21. Our studies demonstrate that members of the bovine prolactin gene family have a close physical association with each other, and all members demonstrate genetic variability in the breeding population.

Placental-specific expression from the mouse placental lactogen II gene promoter

The gene for mouse placental lactogen II (mPL-II) has been isolated and characterized. This gene contains five exons, with a transcription start site 59 nucleotides upstream of the translation initiation ATG. Introduction of a DNA construct containing 2.7 kilobases of sequence upstream of the mPL-II transcription initiation site directed the synthesis of a linked coding region for the simian virus 40 large and small tumor antigens in placental trophoblast giant cells of transgenic mice. The pattern of simian virus 40 transgene expression in the placenta was indistinguishable from that of the endogenous mPL-II gene. In contrast, the first 569 base pairs upstream of the transcription start site proved insufficient to direct placental expression. Thus, one or more elements required for placental trophoblast giant cell expression have been localized to a region between -2700 and -569 of the mPL-II gene.

The ?-subunit of the skeletal muscle sodium channel is encoded proximal to Tk-1 on mouse Chromosome 11

Recent evidence suggests that the human neuromuscular disorders, hyperkalemic periodic paralysis and paramyotonia congenita, are both caused by genetic defects in the alpha-subunit of the adult skeletal muscle sodium channel, which maps near the growth hormone cluster (GH) on Chromosome (Chr) 17q. In view of the extensive homology between this human chromosome and mouse Chr 11, we typed an interspecies backcross to determine whether the murine homolog (Scn4a) of this sodium channel gene mapped within the conserved chromosomal segment. The cytosolic thymidine kinase gene, Tk-1, was also positioned on the genetic map of Chr 11. Both Scn4a and Tk-1 showed clear linkage to mouse Chr 11 loci previously typed in this backcross, yielding the map order: TrJ-(Re, Hox-2, Krt-1)-Scn4a-Tk-1. No mouse mutant that could be considered a model of either hyperkalemic periodic paralysis or paramyotonia congenita has been mapped to the appropriate region of mouse Chr 11. These data incorporate an additional locus into the already considerable degree of homology observed for these human and mouse chromosomes. These data are also consistent with the view that the conserved segment region may extend to the telomere on mouse Chr 11 and on human 17q.

Linkage of loci associated with two pigment mutations on mouse chromosome 13

Progeny from one intra- and two inter-specific backcrosses between divergent strains of mice were typed to map multiple markers in relation to two pigment mutations on mouse chromosome 13, beige (bg) and pearl (pe). Both recessive mutants on a C57BL/6J background were crossed separately with laboratory strain PAC (M. domesticus) and the partially inbred M. musculus stock PWK. The intra- and inter-specific F1 hybrids were backcrossed to the C57BL/6J parental strain and DNA was prepared from progeny. Restriction fragment length polymorphisms were used to follow the segregation of alleles in the backcross offspring at loci identified with molecular probes. The linkage analysis defines the association between the bg and pe loci and the loci for the T-cell receptor gamma-chain gene (Tcrg), the spermatocyte specific histone gene (Hist1), the prolactin gene (Prl), the Friend murine leukaemia virus integration site 1 (Fim-1), the murine Hanukuh Factor gene (Muhf/Ctla-3) and the dihydrofolate reductase gene (Dhfr). This data confirms results of prior chromosomal mapping studies utilizing bg as an anchor locus, and provides previously unreported information defining the localization of the prolactin gene on mouse chromosome 13. The relationship of multiple loci in relation to pe is similarly defined. These results may help facilitate localization of the genes responsible for two human syndromes homologous with bg and pe, Chediak-Higashi syndrome and Hermansky-Pudlak syndrome.

Localization of the panhypopituitary dwarf mutation (df) on mouse chromosome 11 in an intersubspecific backcross

Ames dwarf (df) is an autosomal recessive mutation characterized by severe dwarfism and infertility. This mutation provides a mouse model for panhypopituitarism. The dwarf phenotype results from failure in the differentiation of the cells which produce growth hormone, prolactin, and thyroid stimulating hormone. Using the backcross (DF/B-df/df X CASA/Rk) X DF/B-df/df, we confirmed the assignment of df to mouse chromosome 11 and demonstrated recombination between df and the growth hormone gene. This backcross is an invaluable resource for screening candidate genes for the df mutation. The df locus maps to less than 1 cM distal to Pad-1 (0.85 +/- 0.85 cM). Two new genes localized on mouse chromosome 11, Rpo2-1, and Edp-1, map to a region of conserved synteny with human chromosome 17. The localization of the alpha 1 adrenergic receptor, Adra-1, extends a known region of synteny conservation between mouse chromosome 11 and human chromosome 5, and suggests that a human counterpart to df would map to human chromosome 5.

Localization of the growth hormone gene to the distal half of mouse chromosome 11

A DNA fragment size variant for the growth hormone gene, Gh, has been identified among inbred strains of mice. The inbred strains SM/J and CAST/Ei carry the less frequent allele Ghb and 11 other strains carry the Gha allele. Segregation analysis of data from two crosses involving SM/J and NZB/BINJ and a cross involving BALB/cJ and CAST/Ei confirmed the assignment of Gh to mouse chromosome 11 and placed the locus 2.6 +/- 1.8 map units distal to Erba (avian erythroblastosis oncogene A), a position consistent with the assignment of the Gh locus to the q22-q24 region of chromosome 17 on the human map. Segregation analysis also refined the location of Sparc (secreted acidic cysteine-rich glycoprotein) on mouse chromosome 11 to a position 16.7 +/- 4.2 map units proximal to Evi-2 (ecotropic viral integration site 2).

The Pit-1 transcription factor gene is a candidate for the murine Snell dwarf mutation

Two nonallelic mouse mutations with severe dwarf phenotypes are characterized by a lack of growth hormone, prolactin, and thyroid stimulating hormone. The cells that normally synthesize these pituitary hormones express a common transcription factor called GHF-1 or Pit-1. Using an intersubspecific backcross, we have demonstrated tight linkage of the Pit-1 and Snell dwarf (dw) genes on mouse chromosome 16. No recombination was observed between Pit-1 and dw in 110 individuals examined. Southern blot analysis of genomic DNA reveals that the Pit-1 gene is rearranged in C3H/HeJ-dwJ/dw mice but not in coisogenic +/+ animals, providing molecular evidence that a lesion in the Pit-1 gene results in the Snell dwarf phenotype. Demonstration of low levels of Pit-1 expression in Ames dwarf (df) mice implies that both Pit-1 and df expression may be required for pituitary differentiation.

Genome imprinting phenomena on mouse chromosome 7

Heterozygotes for the reciprocal translocation T(7;15)9H were intercrossed, with albino (c) and underwhite (uw) as genetic markers, in order to study genetic complementation in mouse chromosome 7. Chromosome 15 is known to show normal complementation. Neither reciprocal cross in which one parent was c/c and the other wild type yielded albino progeny at birth although about 17% would be expected, but albino foetuses were recovered when the mother was c/c and father wild type. These products of maternal duplication/paternal deficiency for distal 7 were markedly retarded with small placentae. No albino foetuses were found when the father was c/c and mother wild type, which suggested earlier lethality. Equivalent crosses with uw (chromosome 15) as proximal marker gave normal underwhite progeny when the mother was uw/uw but small placentae, retardation and neonatal death of presumptive underwhites in the reciprocal cross. These abnormal newborn would have had a maternal duplication/paternal deficiency for proximal 7. These and other findings indicate that one region of defective complementation probably lies distal to the breakpoint of T(7;18)50H at 7E2-F2, while another is between the centromere and 7B3. Examination of man-mouse homologies suggests that the loci for three pathological human conditions (Beckwith-Weidemann syndrome, dystrophia myotonia and rhabdomyosarcoma) with differential parental transmission may be located in homologous regions to those affected by imprinting phenomena on mouse chromosome 7.

Assignment of the growth hormone gene locus to 19q26-qter in cattle and to 11q25-qter in sheep by in situ hybridization

The growth hormone gene locus (GH) of cattle and sheep was mapped to a chromosomal region in each species by using in situ hybridization. The probe employed was an 830-bp cDNA sequence from the ovine growth hormone gene. Based on QFQ chromosome preparations, our results show that the GH locus is on cattle chromosome 19 in the region of bands q26-qter and in sheep on chromosome region 11q25-qter. The GH assignments together with previous localizations of type I cytokeratin genes (KRTA) and one homeobox (HOX2) gene in cattle and one type I cytokeratin gene (KRTA) in sheep identify a strongly conserved chromosomal segment on human chromosome 17, bovine chromosome 19, and sheep chromosome 11.

Characterization of a mouse mitogen-regulated protein/proliferin gene and its promoter: a member of the growth hormone/prolactin gene superfamily

A genomic clone containing the complete gene, designated mrp/plf3, of a member of the mitogen-regulated protein/proliferin (MRP/PLF) multi-gene family was isolated from a mouse genomic library constructed in lambda L47.1. The DNA sequences of the 5' flanking region, the exons, and the exon/intron boundaries have been determined. The size and organization of the five exons in the murine mrp/plf3 gene are very similar to those of members of the prolactin/growth hormone family, confirming that mrp/plf3 is a part of this superfamily. Removal of an upstream negative regulatory element revealed an active mrp/plf promoter that was responsive to TGF-alpha and contains known regulatory elements. Intracellular mrp/plf mRNA levels were increased by 17 beta-estradiol and reduced by dexamethasone.